Biasing means for capstan pressure wheel



June 16, 1964 FIG. I

D. L. JOSLOW 3,137,429

BIA-SING MEANS FOR CAPSTAN PRESSURE WHEEL Filed April 26, 1962 INVENTOR.DAVID L. JOSLOW ATTCFNEYS 3,137,429 BIASING MEANS FOR CAPSTAN PRESSUREWHEEL David L. Joslow, Chester, Conn., assignor to Chester ElectronicLaboratories, Incorporated, Chester, Conn., a corporation of ConnecticutFiled Apr. 26, 1962, Ser. No. 190,291 12 Claims. (Cl. 226-176) Thisinvention relates to tape transport mechanisms for magnetic taperecorders and the like and of the type including a continuously rotatingcapstan and a pressure wheel movable into and out of a tape feedingposition b with respect to the capstan at which position the tape issqueezed between the capstan and pressure wheel so as to be frictionallydriven by the capstan. More particularly, this invention deals with abiasing means for the pressure wheel of such transport mechanisms forcontrolling the pressure at which the tape is squeezed against thecapstan and for providing other desirable effects.

The general object of this invention is to provide an improved pressurewheel mechanism for a tape transport device which mechanism includesnovel biasing means for controlling the pressure exerted by the wheelagainst the tape and capstan when the wheel is moved to its tape feedingposition. 7

A more particular object of this invention is to provide a pressurewheel mechanism of the foregoing character wherein the biasing means forthe pressure wheel is adjustable to vary the pressure exerted by thewheel against the tape and capstan and wherein the means for effectingsuch adjustment are accessible from the outside of'the tape transporthousing or the like so that adjustments may be quickly and easily made.

Another object of this invention is to provide a pressure wheelmechanism adapted for operation by a solenoid motor and which mechanismallows for a suificient amount of overtravel of the solenoid plunger topermit the plunger to be drawn into its fully actuated position withrespect to thesolenoid coil when upon actuation of the solenoid thepressure Wheel engages the capstan and tape before the solenoid plungerreaches such fully actuated position.

Other objects and advantages of the invention will be apparent duringthe course of the following description and from the drawing forming apart hereof.

The drawing shows a preferred embodiment of the invention and suchembodiment will be described, but it will be understood that variouschanges may be made from the construction disclosed, and that thedrawing and description are not to be constructed as defining orlimiting the scope of the invention, the claims forming a part of thisspecification being relied upon for that purpose.

Of the drawing:

FIG. 1 is a fragmentary top view of a tape transport device employing apressure wheel mechanism embodying the present invention.

FIG. 2 is a vertical sectional view taken on the line 2-2 of FIG. 1.

FIG. 3 is a vertical sectional view taken generally on the line 33 ofFIG. 2.

FIG. 4 is a fragmentary sectional view taken on the line 4-4 of FIG. 3.

FIG. 5 is a fragmentary sectional view taken on the line 55 of FIG. 3.

Turning now to the drawings, FIG. 1 is a fragmentary top view of a tapetransport device of the type used, for.

face member 12 in the form of a generally flat sheet and which member isshown to be and is referred to hereinafter as being horizontal. Otherparts of the device are likewise shown and sometimes referred to hereinas being horizontal or vertical, but it is to be understood that theseterms are used only to define the relative orientations of the parts oneto another and that in use the upper surface member 12 need notnecessarily be horizontal.

Included in the tape transport device is a vertical capstan 14 which asshown in FIG. 2 extends upwardly beyond the upper surface member 12,passing through an opening 16 therein, and also extends downwardlythrough an opening 18 in a base plate 20-located some distance below theupper surface member. Suitable means (not shown) are associated with thecapstan 14 for rotating the same continuously about its vertical centralaxis as is well known in the art. Other means (not shown) are alsoemployed in the transport device for guiding the tape 10 along a pathwhich passes in close proximity to the capstan 14.

Feeding of the tape 10 is accomplished by the capstan 14 in cooperationwith a pressure wheel 22 located on the opposite side of the tape 10from the capstan 14 so that the tape passes between the capstan and thepressure wheel. The, pressure wheel is supported for rotation about avertical axis and is movable in a horizontal plane so as to be broughtinto and out of a tapeieeding relationship with the capstan. In FIGS. 1and 2 the pressure wheel is shown out of tape feeding relationship withthe capstan. Under this condition "the pressure wheel is spaced somedistance from the capstan so that the tape 10 very lightly engages thecapstan, if at all, and has no drivingforce imparted thereto. To causefeeding movement of the tape the pressure wheel 22 is moved toward thecapstan 14 sothat the tape is. squeezed with some force between thecapstan and the pressure wheel. The friction thereby created between thetape and capstan will cause the capstan to move the tape and this willbe accompanied by rotation of the pressure wheel.

The force with which the pressure wheel is held against the capstanduring a tape feeding operation is of considerable importance since itisnecessary that the wheel exert suflicient pressure on the tape toprevent slippage between the tape and capstan. On the other hand, it isalso desirable that this force be held to as low a value as possible toprevent undue loads on the bearings and the like supporting the capstan.The present invention, therefore, concerns, among other things, anactuating means for moving the pressure wheel into and out of its tapefeeding position and for permitting adjustment of the force exerted bythe pressure wheel against the capstan so that s gh force may beselectively adjusted to an optimum v ue.

Referring to FIGS. 1, 2, and 3, the actuating mechanism for the pressurewheel 22 in the present instance includes a vertical shaft 24 supportedby the base plate 20 for pivotal movement about a vertical axis. In thepresent case, the supporting means for the shaft 24 includes ashouldered bushing 26 which is fitted into an opening in the base plateand which rotatively receives a corresponding portion of the shaft 24.Above the bushing 26 the shaft includes a radial flange 28 defining adownwardly facing surface which seats on the shoulder of the bushing 26to vertically support the shaft 24. The shaft 24 is 'axilaly retained inthe base plate 20 by the flange 28 located above the base plate and by asnap ring 30, or the like, located below the base plate. The shaft 24extends upwardly from the base plate 20 and passes upwardly through anopening in the upper surface member 12 and for some distance upwardlybeyond said latter member. The shaft also has a lower portion whichextends some-distance downwardly from the base plate.

Between the top surface member 12 and the base plate Patented June 16,1964 portion of the actuating mechanism for the pressure wheel.

22 is therefore concealed below the surface member 12.

From the foregoing description it will be understood that by rotatingthe shaft 24 about its vertical axis, the pressure wheel 22 may bebrought into and out of its tape feeding relationship with the capstan14. This movement of the shaft 24 is in turn effected by an actuatingmember which is rotatable about the axis'of the shaft 24 and by biasingmeans between the actuating member and the shaft. In the illustratedcase the actuating member comprises a horizontal arm 38 carried by the.lower end of the shaft 24 and movable angularlyrelative thereto andhaving its outer end connected through a link 46 to the plunger 42 of asolenoid motor 44. As mentioned, the actuating arm 38 is connected tothe shaft 24 through a resilient biasing means which acts to tend tohold the arm 38 in a given normal angular position on the shaft 24 asdefined by suitable stop means and to resist angular movement of the armrelative to the shaft away from such normal position against the biasingforce. The arrangement of the stop means and the biasing means is suchthat the resilient movement of the arm 38 relative to the shaft 24 andaway from its normal position is in the same direction as that in whichthe shaft is rotated to bring the pressure wheel into tape feedingrelationship with the capstan. Therefore, upon movement of the actuatingarm, in the direction corresponding to movement of the pressure wheeltoward the capstan the actutaing arm may move relative to the shaft andagainst the force of the biasing means after movement of the shaft andarm 32 is arrested by the capstan.

By way of further explanation, FIG. 1 shows the actuating arm 38 in itsnormal position relative to the shaft 24 and relative to the arm 32 andfurther shows the pressure wheel 22 spaced from the capstan 14 by adistance greater than the thickness of the tape so as to be out of tapefeeding relationship with the capstan. This condition is achieved whenthe solenoid motor is de-ener gized. If the solenoid motor is nowenergized the plunger 42 is drawn into the solenoid, or to the left asviewed in FIG. 1, which through the link 40 moves the arm 38 toward theleft to rotate the shaft 24 in a counterclockwise direction about itscentral axis. This movement of the shaft 24 in turn rotates the arm 32in a counterclockwise direction to move the pressure wheel 22 toward thecapstan 14 and to squeeze the tape 10 between the pressure wheel and thecapstan to cause feeding movement of the tape. As the pressure wheelreaches this tape feeding position further movement of it, the arm 32,and

the shaft 24 is prevented by the capstan. When this occurs, however, thesolenoid plunger 42 is not in its fully actuated position, and thereforefurther movement of the plunger toward the left is obtained by movementof the actuating arm 38 in a counterclockwise direction relative to theshaft 24 and against the force of the biasing means. This permits theplunger 42 to move to its fully actuated position relative to thesolenoid coil at which the solenoid draws a minimum amount of current,

thereby preventing overheating of the solenoid. The use 7 4 force andthereby the force exerted by the pressure wheel on the capstan when theactuating arm is moved to its fully actuated position. Also, the meansfor effecting such adjustment are preferably accessible from the outsideof the transport device so that the pressure exerted by the pressurewheel may be readily and easily varied without the necessity ofdismantling any portions of the device. As shown best in FIGS. 2, 3, and4, the actuat ing arm 38 is carried by the lower end portion of theshaft 24 which portion is provided with two parallel flats 46, 46. Thearm'38 is provided with an opening, which loosely receives the shaft 24,and has associated there'- withtwo screws 48, 48, the inner ends ofwhich protrude some distance into the associated opening so as toprovide stopmeans for limiting the angular movement of the aim.

38 relative to the shaft 24 by engagement with the flats.

In FIG. 4 the solid lines show the arm 38 in one limit of its movementrelative to the shaft 24 and the broken lines show the same arm in theother limit of its movement relative to the shaft 24. It will beunderstood, however, that the illustrated stop means has been shown by fA way of example only and that other suitable means may be employedwithout departing fromthe invention. It will also be understood that inaccordance with the invention it is necessary to limit the movement ofthe arm 38 in one direction only with respect to the shaft, suchlimitdefining the normal position of the arm relative to the shaft. The shaft24 is tubular and extending through the bore thereof is an adjustingmember in the form of a bolt 50 threaded along its entire length andhaving a slotted head 52 at itsupper end, which slotted head serves as ameansfor rotating the bolt. Threadably received on the bolt 50 betweenthe head 52 and the upper end of the shaft 24 is a nut 54 which in theillustratcd case is generally cylindrical in shape and includes one ormore radial openings such as indicated partially at'55 for receiving aspanner wrench forv turning the. same At its lowerend the bolt 50 .ex-.

relative to the bolt. tends downwardly beyond the lower end of the shaft24 and threadably receives two nuts 56 and 58 which are spaced somedistance apart on the bolt and between.

hold the bolt 50 in any selected angular position relative to the shaft24. The lower nut 58 serves to retain the spring 60 on the bolt 50.

The lower end of .the bolt 50 has an axial slot which receives one end62 of the coil spring 60 to restrain the same from rotation relative tothe bolt. The other end of the spring is in the form of an arm 64 whichextends i outwardly from the bolt 50 and hooks partially around adownwardly extending finger 66-attached to the actu-; ating arm 38.From. this it will be appreciated that the spring 60, if under tension,tends to rotate the arm 38 relative to the bolt 50 and likewise relativeto the shaft 24, assuming the shaft to be fixed relative to the, bolt.

This rotation is, however, limited by the stop means de-. 1 scribedabove and shown'in FIG. 4 so that the arm 38 is held in or urged towardits normal position by the spring. The initial tension or preload in thespring will determine the amount of force required to move the arm.38away from its normal position and this in turn will determine thepressure exerted by the pressure wheel on the capstan when the pressurewheel is moved into its tape feeding position.

The initial tension or preload exerted by the spring 60 The nut 56serves to provide a radial abut- Therefore by holding The upper nut 54is therefore seen to comprise a releasable locking means which may beoperated to may be varied by rotating the bolt or adjusting member 50relative to the shaft 24, this having the effect of twisting the one end62 of the spring relative to the other end 64. This is accomplished byloosening the nut 54 to unlock the bolt from the shaft, then rotatingthe head of the bolt 52 to the point at which the desired tension isachieved, and thereafter retightening the nut 54 to lock the bolt in itsnew position relative to the shaft.

In the illustrated case this adjusting operation is easily performedthrough the use of a screwdriver and a spanner Wrench. The screwdriveris first entered into the slot of the bolt head 52 and the spannerwrench applied to the nut 54. The nut 54 is then turned by means of thespanner wrench to unlock the bolt 50. The screwdriver is then rotated ina counterclockwise direction until the desired amount of tension isobtained, rotation of the arm 32 and shaft 34 being prevented byengagement of the pressure wheel 22 with the capstan 14 during thisoperation. The nut 54 is thereafter retightened against the shaft 24while the screwdriver is used to hold the bolt in its adjusted position.

Although in the present instance the adjusting member 59 has been shownto be provided with a slotted head 52 for receiving a screwdriver andthe locking member 54 has been shown in the form of a nut adapted foruse with a spanner wrench, it will be understood that the invention isnot necessarily limited to this particular design of these elements. Ifdesired, each of these parts may, in fact, be made of such a size andshape as to be directly manipulable by the hands of a user without theneed for tools.

The invention claimed is:

1. In a tape transport device having a capstan located adjacent the pathof tape travel and supported for rotation about its central axis, thecombination comprising a shaft supported for rotation about an axisfixed relative to and disposed parallel with said capstan axis, an armfixed to said shaft and having a pressure wheel supported thereon forrotation about an axis fixed relative to said arm in parallelrelationship with said capstan axis which pressure wheel is moved towardsaid capstan and into tape feeding relationship therewith as said shaftis moved angularly in a first direction and is moved away from saidcapstan as said shaft is moved angularly in the oppo site direction, anactuating member supported for pivotal movement about the axis of saidshaft and relative to said shaft, stop means for limiting saidpivotalrnovement of said actuating member in said opposite directionrelative to said shaft, biasing means for urging said actuating memberin said opposite direction and toward its limited position relative tosaid shaft and for resiliently resisting movement of said actuatingmember in said first direction relative to said shaft whereby uponmovement of said actuating member in said first direction said actuatingmember may move relative to said shaft and against theforce of saidbiasing means after movement of said shaft and arm is arrested by saidcapstan.

2. The combination as defined in claim 1 further characterized by saidactuating member comprising an arm loosely carried by said shaft, andmeans connected with said arm and including a solenoid motor for movingsaid latter arm about said axis of said shaft between actuated andunactuated positions.

3. The combination as defined in claim 1 further characterized by saidbiasing means comprising a spring, and means for selectively adjustingthe preload of said spring without changing said limited position ofsaid actuating member relative to said shaft to vary the amount of forcerequired to move said actuating member relative to said shaft and awayfrom said limited position.

4. The combination as defined in claim 3 further characterized by saidtape transport device having a top surface member, said pressure wheelbeing located above said top surface member and said actuating memberbeing located below said top member, and said means for selectively:adjusting the preloadof said spring in: cluding parts located abovesaid'top surface member which parts are manually operable to effect saidadjust ment. a v 5. In a tape transport device ,having a capstan locatedadjacent the path of tape travel and supported for rotation about avertical axis, the combination comprising a hollow shaft supported forrotation about a vertical axis spaced from said capstan axis, an armfixed to said shaft and having a pressure wheel supported thereon forrotation about a vertical axis also spaced from said capstan axis andwhich pressure wheel'is moved toward said capstan and into tape feedingrelationship therewith as said shaft is moved angularly in a firstdirection andv is moved away from said capstan as said shaft is movedangularly in the opposite direction, an actuating member supported forpivotal movement about the axis of said shaft and relative to saidshaft, stop means for limiting said pivotal movement of saidactuatingmember. in said opposite direction relative to said shaft, an adjustingmember extending vertically through the bore of said shaft and havingmeans atits upper end for rotating the same relative tosaid'shaft,'meansfor releasably locking said adjusting member in variousselected angular positions relative to said shaft, and a torsion springhaving one end fixed relative to said actuating member and its other endfixed relative to said adjusting member and which spring is arranged soasv to resiliently urge said actuating member in said opposite directionrelative to said shaft when said adjusting member is angularly locked tosaid shaft and the initial tension of which spring may therefore bevaried by varying the angular position of said adjusting member relativeto said shaft.

6. The combination defined in claim 5 further characterized by saidadjusting member having a threaded portion adjacent its upper end end,and said releasable locking means including means defining an abutmenton the lower end portion of said adjusting member which abutment isengageable with the lower end of said shaft and said releasable lockingmeans also including a locking member threadably received on saidthreaded portion of said adjusting member which locking member by beingthreaded in one direction or another on said adjusting member is movableaxially of said adjusting member and into and out of a position at whichsaid locking member engages the upper end of said shaft and clamps thelatter between itself and said abutment to prevent angular movement ofsaid adjusting member relative to said shaft.

7. The combination as defined in claim 5 further characterized by saidactuating member comprising an arm loosely received on a correspondingportion of said shaft for pivotal movement relative to said shaft.

8. The combination as defined in claim 5 further characterized by saidtorsionxspring comprising a helical coil spring surrounding saidadjusting member adjacent the lower end thereof.

9. The combination as defined in claim 5 further characterized by meansconnected with said actuating member and including a solenoid motorhaving a plunger for tmoving said actuating member about said axis ofsaid shaft between actuated and unactuated positions corresponding toactuated and unactuated positions respectively of said plunger, saidactuating member in being moved from said unactuated position to saidactuated position being movedtin said first direction to an extentgreater than that necessary to bring said pressure wheel into tapefeeding relationship with said capstan so that said actuating member ismoved relative to said shaft against the force of said spring.

10. In a tape transport device having a capstan located adjacent thepath of tape travel and supported for rotation about a vertical axis,the combination comprising a hollow shaff supported for rotation about avertical axis spaced from said capstan axis, an arm fixed to said shaftand having a pressure wheel supported thereon for rotation about avertical axis also spaced from said capstan axis and which pressurewheel is moved toward said capstan and into tape feeding relationshiptherewith as said shaft is moved angularly in a first direction and ismoved away from said capstan as said shaft is moved angularly in theopposite direction, an actuating arm loosely supported on the lower endportion of said shaft for relative pivotal movement about the axis ofsaid shaft, stop means for limiting said pivotal movement of saidactuating arm in said opposite direction relative to said shaft, anadjusting member extending vertically through the bore of said shaft andbeyond the upper ends thereof and having means at its upper end forrotating the same relative to said shaft, means for releasably lockingsaid adjusting member in various selected angular positions relative tosaid shaft, and a helical coil spring axially retained on andsurrounding one end of said adjusting member and having one end fixedrelative to said actuating arm and its other end fixed relative to saidadjusting member and which spring is arranged so as to resiliently urgesaid actuating arm in said opposite direction relative to said shaftwhen said adjusting member is angularly locked to said shaft and theinitial tension of which spring may therefore be varied by varying theangular position of said adjusting member relative to said shaft.

11. The combination defined in claim 10 further characterized by saidadjusting member comprising a bolt, threaded along substantially itsentire length, and'said releasable locking means comprising upper andlower members threadably received by said bolt and ,engag'eablerespectively with the upper and lower end surfaces of i said shaft.

12. The combination as defined in claim 11 further characterized by saidmeans for rotating said adjusting member comprising a slotted head onsaid bolt.

References Cited in the file of this patent UNITED STATES PATENTS LaksoJan. 8, i957

1. IN A TAPE TRANSPORT DEVICE HAVING A CAPSTAN LOCATED ADJACENT THE PATHOF TAPE TRAVEL AND SUPPORTED FOR ROTATION ABOUT ITS CENTRAL AXIS, THECOMBINATION COMPRISING A SHAFT SUPPORTED FOR ROTATION ABOUT AN AXISFIXED RELATIVE TO AND DISPOSED PARALLEL WITH SAID CAPSTAN AXIS, AN ARMFIXED TO SAID SHAFT AND HAVING A PRESSURE WHEEL SUPPORTED THEREON FORROTATION ABOUT AN AXIS FIXED RELATIVE TO SAID ARM IN PARALLELRELATIONSHIP WITH SAID CAPSTAN AXIS WHICH PRESSURE WHEEL IS MOVED TOWARDSAID CAPSTAN AND INTO TAPE FEEDING RELATIONSHIP THEREWITH AS SAID SHAFTIS MOVED ANGULARLY IN A FIRST DIRECTION AND IS MOVED AWAY FROM SAIDCAPSTAN AS SAID SHAFT IS MOVED ANGULARLY IN THE OPPOSITE DIRECTION, ANACTUATING MEMBER SUPPORTED FOR PIVOTAL MOVEMENT ABOUT THE AXIS OF SAIDSHAFT AND RELATIVE TO SAID SHAFT, STOP MEANS FOR LIMITING SAID PIVOTALMOVEMENT OF SAID ACTUATING MEMBER IN SAID OPPOSITE DIRECTION RELATIVE TOSAID SHAFT, BIASING MEANS FOR URGING SAID ACTUATING MEMBER IN SAIDOPPOSITE DIRECTION AND TOWARD ITS LIMITED POSITION RELATIVE TO SAIDSHAFT AND FOR RESILIENTLY RESISTING MOVEMENT OF SAID ACTUATING MEMBER INSAID FIRST DIRECTION RELATIVE TO SAID SHAFT WHEREBY UPON MOVEMENT OFSAID ACTUATING MEMBER IN SAID FIRST DIRECTION SAID ACTUATING MEMBER MAYMOVE RELATIVE TO SAID SHAFT AND AGAINST THE FORCE OF SAID BIASING MEANSAFTER MOVEMENT OF SAID SHAFT AND ARM IS ARRESTED BY SAID CAPSTAN.